This invention relates to a heat-treating device for safely and efficiently heat-treating product to be treated at relatively low temperature such as lower than 100.degree. C. with reduced pressure steam and/or water as heat medium.
In the field of chemical and food industries, materials are frequently treated at relatively low temperature lower than 100.degree. C., for example, in order to maintaining safe operation and product quality. For such heat-treatment, such a device as disclosed, for example, in the Japanese patent opening gazette No. 60-64108, which uses reduced pressure steam as heat medium, has been used. In this device, steam is supplied from a steam source through a pressure reducing valve to a heat exchanger chamber having an outlet connected to a conventional vacuum pump through a steam trap which is bypassed for enabling flow-rate control of the fluid path. However, the conventional vacuum pump is operated always to attain its ultimate vacuum pressure, so that the steam is excessively sucked by the pump to give an undesirably high degree of vacuum to the heat exchager chamber. In order to prevent such a trouble, the flow-rate of the above-mentioned bypass may be increased for maintaining the pressure within the heat exchanger chamber. As a result, however, a lot of steam is exhausted through the bypass to result not only in an excessive loss of steam but also in an unstable pressure within the heat exchanger chamber.
Accordingly, an object of this invention is to provide an improved reduced pressure steam heat treating device which exhibits a steady steam pressure in the heat exchanger chamber and a high thermal efficiency.
Another object of this invention is to provide a convenient heat-treating device which can effect alternating heating and cooling operations as occasion demands.